Insertion loss is defined as the difference between the optical power launched into an interconnection cable and the optical power measured at the opposite end, or mathematically as follows: L.sub.i =-10 log P.sub.out /P.sub.in, where L.sub.i is the insertion loss, P.sub.in is the power of the optical signal launched into a cable, and P.sub.out is the power of the optical signal as it passes out of the cable. The geometric factors which influence insertion loss at a fiber-to-fiber interconnection include transverse offset, longitudinal offset, angular offset, index of refraction mismatch, mode field radius mismatch, the shape and finish of the fiber endface, and physical damage that may be present at the endface of the fiber in the connector.
Current methods of measuring insertion loss require that a reference jumper be identified and interconnected to the connector endface under test. The optical power exiting the reference end is measured and then compared with the optical power exiting the opposite end of the jumper under test. When taking the measurement, it is assumed that all of the loss is attributable to the jumper endface under test and none of the loss is attributable to the reference endface.
Although meritorious to an extent, this method is unsatisfactory in that variations in the reference endfaces often contributes to measurement error. Identification and maintenance of reference jumpers is a costly process, and the method itself is labor intensive. Furthermore, in order to automate measurement of insertion loss in a fully automated assembly line, automatic and contactless measurement is necessary. To date, no systems are known in the industry for contactlessly and automatically determining the insertion loss of an optical fiber connector.